JP5355378B2 - Rubber composition for anti-vibration rubber and anti-vibration rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for vibration-proof rubber which has achieved both reduction in dynamic-to-static modulus ratio and improvement in durability, and to provide a vibration-proof rubber. <P>SOLUTION: The rubber composition for vibration-proof rubber obtained by mixing a carbon black-containing slurry solution and natural rubber latex in a liquid phase, followed by drying, includes carbon black having a CTAB specific surface area (m<SP>2</SP>/g) of 20-55, and has a dispersion degree of the carbon black measured according to ASTM D 2663-69 (B method) in the rubber composition for vibration-proof rubber of 98% or more. Further, the number-average molecular weight of natural rubber in the rubber composition for vibration-proof rubber is 1,800,000 or more. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a rubber composition for vibration proof rubber and vibration proof rubber, and more particularly to a rubber composition for vibration proof rubber that can be suitably used as a vibration proof member for an engine mount for automobiles, and a vibration proof rubber using the same. Is.

  Conventionally, natural rubber blended with carbon black as a reinforcing material has been used as an anti-vibration rubber. In recent years, anti-vibration rubber, especially automobile anti-vibration rubber, requires a high level of both reduction of dynamic magnification (dynamic spring constant / static spring constant) and improvement of durability. Has been.

  In order to reduce the dynamic magnification of the vibration-proof rubber, it is important to improve the dispersibility of carbon black in natural rubber. Conventionally, a method of increasing the dispersibility of carbon black in natural rubber by using carbon black having a large particle size has been adopted, but this method tends to impair the durability of the vibration-proof rubber. there were.

  On the other hand, in order to increase the dispersibility of carbon black in natural rubber, for example, there is a method of increasing the dispersibility of carbon black by increasing the kneading time in Banbury and increasing the number of kneading times. Due to the heat history during mixing, the molecular weight of the natural rubber decreased, and the toughness (durability), which is an advantage of the natural rubber, tended to be impaired. In addition, even if kneading is sufficiently carried out, the dispersibility of carbon black is still insufficient, and it is difficult to achieve a high level of both a low dynamic magnification and improved durability of vibration-proof rubber. there were.

In the following Patent Document 1, a vulcanized rubber of a natural rubber wet masterbatch rubber composition in which carbon black having a CTAB specific surface area (m ² / g) of more than 60 is blended with natural rubber is resistant to fracture and crack growth. It is described that it is optimal for steel-coated rubber for tires and industrial rubber products because of its excellent properties. However, such a document does not describe or suggest a reduction in the dynamic ratio of vibration-proof rubber and an improvement in durability, and carbon black having a CTAB specific surface area (m ² / g) exceeding 60 is excellent in reinforcement. Since the particle size of the product is too small, the dynamic ratio cannot be reduced with the vulcanized rubber of the rubber composition containing this.

  Patent Document 2 below describes a method for producing a natural rubber masterbatch that is mixed with carbon black while decomposing an amide bond of natural rubber. The purpose of this production method is to reduce the Mooney viscosity of the rubber composition by decomposing the amide bond of the natural rubber, thereby improving the processability of the rubber composition. However, in the natural rubber masterbatch described in the literature, the toughness (durability) of the natural rubber tends to deteriorate due to the decrease in the molecular weight of the natural rubber. For this reason, when anti-vibration rubber is manufactured from the natural rubber masterbatch described in this literature, the durability of the anti-vibration rubber tends to deteriorate.

JP 2006-213804 A JP 2004-99625 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a rubber composition for vibration-proof rubber and a vibration-proof rubber that achieve both reduction in dynamic magnification and improvement in durability. .

  In order to solve the above problems, the present inventors have improved the dispersibility while optimizing the particle size of carbon black blended in natural rubber, and suppressing the decrease in the molecular weight of natural rubber. I found that the problem could be solved. The present invention has been made as a result of the above-described studies, and achieves the above-described object with the following configuration.

That is, the rubber composition for vibration-proof rubber according to the present invention is a rubber composition for vibration-proof rubber obtained by mixing a carbon black-containing slurry solution and natural rubber latex in a liquid phase and drying. Has a CTAB specific surface area (m ² / g) of 20 to 55 and a carbon black dispersity measured in accordance with ASTM D2663-69 (Method B) in the rubber composition for vibration-proof rubber. The natural rubber has a number average molecular weight of 1,800,000 or more.

  The rubber composition for anti-vibration rubber according to the present invention is obtained by mixing a carbon black-containing slurry solution and natural rubber latex in a liquid phase and drying, thereby causing a decrease in the molecular weight of natural rubber. Therefore, the dispersibility of carbon black can be improved. Specifically, ASTM D2663-69 (Method B) in the rubber composition for vibration-proof rubber is maintained while keeping the number average molecular weight of the natural rubber in the rubber composition for vibration-proof rubber after drying at 1.8 million or more. The degree of dispersion of carbon black measured according to the standard can be 98% or more. Thereby, it is possible to reduce the dynamic magnification and improve the durability of the vibration-proof rubber.

Further, since the carbon black contained in the rubber composition for vibration-proof rubber according to the present invention has a CTAB specific surface area (m ² / g) of 20 to 55, in the vibration-proof rubber obtained from this rubber composition, The magnification can be reduced. If the CTAB specific surface area (m ² / g) of the carbon black is less than 20 (the particle size of the carbon black is too large), even if the dispersibility of the carbon black is increased, a reduction in the dynamic ratio of the anti-vibration rubber can be achieved. The durability is deteriorated. On the other hand, if it exceeds 55 (the particle size of the carbon black is too small), it is impossible to achieve a low dynamic magnification of the vibration-proof rubber.

  As described above, the rubber composition for vibration-proof rubber according to the present invention is improved by optimizing the particle size of the carbon black compounded in the natural rubber, improving its dispersibility, and suppressing the reduction in the molecular weight of the natural rubber. With a product, it is possible to achieve both reduction in dynamic magnification and improvement in durability.

  The anti-vibration rubber according to the present invention is obtained by vulcanizing and molding the rubber composition for anti-vibration rubber described above. With such an anti-vibration rubber, it is possible to achieve both reduction in dynamic magnification and improvement in durability. For this reason, it can be suitably used as an anti-vibration rubber for automobiles such as engine mounts, torsional dampers, body mounts, cap mounts, member mounts, strut mounts, and muffler mounts.

  The rubber composition for vibration-proof rubber according to the present invention is obtained by mixing a carbon black-containing slurry solution and natural rubber latex in a liquid phase and drying.

  The carbon black-containing slurry solution can be produced by mixing carbon black and a dispersion solvent. As a method of mixing carbon black and a dispersion solvent, a general dispersing machine such as a high shear mixer, a high shear mixer, a homomixer, a ball mill, a bead mill, a high pressure homogenizer, an ultrasonic homogenizer, or a colloid mill is used. The method of making it disperse | distribute is mentioned.

  The "high shear mixer" is a mixer having a rotor and a stator, and the rotor rotates with a precise clearance between a rotor capable of high-speed rotation and a fixed stator. Means a mixer with a high shearing action. In order to produce such a high shearing action, it is preferable that the clearance between the rotor and the stator is 0.8 mm or less and the circumferential speed of the rotor is 5 m / s or more. A commercial item can be used for such a high shear mixer, for example, “High Shear Mixer” manufactured by SILVERSON.

  As the dispersion solvent, it is particularly preferable to use water, but for example, water containing an organic solvent may be used.

As carbon black for adjusting a carbon black containing slurry solution, what has a CTAB specific surface area (m < ² > / g) is 20-55 is used. Commercially available products can be used as carbon black having a CTAB specific surface area (m ² / g) within this range, and examples thereof include FEF, GPF, and SRF. The carbon black may be a granulated carbon black granulated in the ordinary rubber industry in consideration of its handling properties, or may be an ungranulated carbon black.

  The carbon black concentration in the carbon black-containing slurry solution is not particularly limited, but is preferably 1 to 20% by weight, and more preferably 3 to 10% by weight.

  In the present invention, when a carbon black-containing slurry solution containing a surfactant is used as a raw material, it is possible to finally produce a rubber composition with better carbon black dispersibility. As the surfactant, known surfactants in the rubber industry can be used, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. It is done. Further, instead of the surfactant or in addition to the surfactant, an alcohol such as ethanol may be added to the carbon black-containing slurry solution. Also in this case, a carbon black-containing slurry solution having excellent carbon black dispersibility can be obtained.

  The natural rubber latex solution is a natural product produced by the metabolic action of plants, and a natural rubber / water system is particularly preferred in which the dispersion solvent is water. The number average molecular weight of the natural rubber in the natural rubber latex used in the present invention is preferably 2 million or more, and more preferably 2.5 million or more.

  In the rubber composition for vibration-proof rubber according to the present invention, a synthetic rubber latex solution may be used in combination with the natural rubber latex solution as long as the durability of the vibration-proof rubber is not impaired. Examples of the synthetic rubber latex solution include those produced by emulsion polymerization of styrene-butadiene rubber, butadiene rubber, nitrile rubber, and chloroprene rubber. However, in order to maintain the durability of the anti-vibration rubber derived from natural rubber, the compounding amount of the synthetic rubber in the rubber composition for anti-vibration rubber is 40% by weight or less in the rubber component (dry weight). It is preferable.

  The method of mixing the carbon black-containing slurry solution and the natural rubber latex in the liquid phase is not particularly limited, and the carbon black-containing slurry solution and the natural rubber latex are mixed with a high shear mixer, high shear mixer, homogenizer. Examples of the mixing method include a general disperser such as a mixer, a ball mill, a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, and a colloid mill. If necessary, the entire mixing system such as a disperser may be heated during mixing.

  The rubber composition for vibration-proof rubber according to the present invention is obtained by mixing a carbon black-containing slurry solution and natural rubber latex in a liquid phase and then drying. This drying method includes coagulant containing a coagulant in a carbon black-containing natural rubber latex solution obtained by mixing a carbon black-containing slurry solution and a natural rubber latex solution in a liquid phase. A drying method may be used, and a drying method may be used in which drying is performed without solidification.

  As a coagulant used in the coagulation drying method, an acid such as formic acid and sulfuric acid usually used for coagulation of a rubber latex solution, and a salt such as sodium chloride can be used.

  As a method for drying the carbon black-containing rubber latex solution, various drying devices such as an oven, a vacuum dryer, and an air dryer can be used.

  In the present invention, a flocculant is contained in a carbon black-containing rubber latex solution obtained by mixing a carbon black-containing slurry solution and a rubber latex solution in a liquid phase, and then the obtained aggregate is obtained. It may be recovered and dried. As the flocculant, known rubber flocculant flocculants can be used without limitation, and specific examples thereof include cationic flocculants.

  In the rubber composition for vibration-proof rubber according to the present invention, the carbon black content after drying is in the range of 20 to 120 parts by weight, preferably 30 to 100 parts by weight with respect to 100 parts by weight of the rubber component. Yes, more preferably 30-60 parts by weight. If the blending amount is less than 20 parts by weight, the reinforcing effect of carbon black cannot be sufficiently obtained. If the blending amount exceeds 120 parts by weight, exothermic properties, rubber mixing properties, workability during processing, and the like are deteriorated.

  In the rubber composition for vibration-proof rubber according to the present invention, it is important that the degree of dispersion of carbon black measured in accordance with ASTM D2663-69 (Method B) is 98% or more. In this case, high dispersibility of the carbon black in the vibration-insulating rubber composition can be ensured, so that the dynamic ratio of the vibration-insulating rubber can be lowered and the durability can be improved.

  The rubber composition for vibration-proof rubber according to the present invention comprises a sulfur-based vulcanizing agent and a vulcanization accelerator together with a masterbatch obtained by mixing a carbon black-containing slurry solution and natural rubber latex in a liquid phase and drying. Conventional rubber industry such as silica, silane coupling agent, zinc oxide, stearic acid, vulcanization accelerator, vulcanization retarder, organic peroxide, anti-aging agent, softener such as wax and oil, processing aid In the range which does not impair the effect of this invention, it can mix | blend suitably and can be used.

  Sulfur as the sulfur-based vulcanizing agent may be normal sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The sulfur content in the rubber composition for vibration-proof rubber according to the present invention is preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the rubber component. If the sulfur content is less than 0.1 parts by weight, the crosslinking density of the vulcanized rubber will be insufficient and the rubber strength will be reduced. If it exceeds 3 parts by weight, both heat resistance and durability will be deteriorated. . In order to ensure good rubber strength of the vulcanized rubber and to further improve the heat resistance and durability, the sulfur content is 0.1 to 2.0 parts by weight with respect to 100 parts by weight of the rubber component. Is more preferably 0.5 to 1.5 parts by weight.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone anti-aging agent, a monophenol anti-aging agent, a bisphenol anti-aging agent, a polyphenol anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture.

  The rubber composition for vibration-proof rubber of the present invention comprises carbon black and natural rubber, if necessary, sulfur vulcanizing agent, vulcanization accelerator, silica, silane coupling agent, zinc oxide, stearic acid, vulcanization acceleration. Auxiliaries, vulcanization retarders, organic peroxides, anti-aging agents, softeners such as wax and oil, processing aids, kneading machines used in the normal rubber industry such as Banbury mixers, kneaders and rolls. It is obtained by using and kneading.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than a vulcanizing component such as a sulfur vulcanizing agent and a vulcanization accelerator is previously kneaded to obtain a master batch, and the remaining components are added. Any of a method of further kneading, a method of adding and kneading each component in an arbitrary order, a method of adding all components simultaneously and kneading may be used.

  By kneading and molding each of the above components, followed by vulcanization, it is possible to produce a vibration-proof rubber that achieves both reduction in dynamic magnification and improvement in durability. Such anti-vibration rubber includes anti-vibration rubber for automobiles such as engine mounts, torsional dampers, body mounts, cap mounts, member mounts, strut mounts, and muffler mounts, as well as anti-vibration rubbers for railway vehicles and industrial machinery Anti-vibration for rubber, building-isolated rubber, seismic-isolated rubber bearings, etc., and can be used suitably for seismic-isolating rubber, especially for automobile mounts such as engine mounts that require both vibration-isolating performance and durability It is useful as a rubber component.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Preparation of rubber composition)
Examples 1-3 and Comparative Examples 2-4
A carbon black-containing slurry solution and natural rubber latex were mixed in a liquid phase and dried to produce a masterbatch containing natural rubber and carbon black. The upper part of Table 1 shows the compounding amount of carbon black with respect to 100 parts by weight of the rubber component after drying, the number average molecular weight of natural rubber in the master batch, and the degree of dispersion (%) of carbon black.

  Next, various compounding agents are added to the produced master batch, and carbon black is further blended as necessary, and kneaded using a normal Banbury mixer to prepare rubber compositions of Examples 1 to 3 and Comparative Examples 2 to 4 did. Table 1 shows the compounding amounts of various compounding agents with respect to 100 parts by weight of the rubber component after drying.

Comparative Example 1
A masterbatch containing natural rubber and carbon black was produced by mixing natural rubber and carbon black in the solid phase in the formulation shown in Table 1. Furthermore, various compounding agents were blended and kneaded using a normal Banbury mixer to prepare the rubber composition of Comparative Example 1. The number average molecular weight of the natural rubber and the dispersity (%) of the carbon black after mixing the natural rubber and carbon black in the solid phase are shown in the upper part of Table 1.

The carbon black, natural rubber, and various compounding agents used are as follows.
a) Natural rubber RSS # 3 Number average molecular weight 2.1 million b) Carbon black (A) FEF ("Seast SO", manufactured by Tokai Carbon Co., Ltd.) CTAB specific surface area (m ² / g) 45
(B) HAF ("Seast 3", manufactured by Tokai Carbon Co., Ltd.) CTAB specific surface area (m ² / g) 81
(C) GPF ("Seast G", manufactured by Tokai Carbon Co., Ltd.) CTAB specific surface area (m ² / g) 28
(D) FT (“Niteron # 15”, manufactured by Nisshin Carbon Co., Ltd.) CTAB specific surface area (m ² / g) 17
c) Zinc oxide No. 3 zinc white d) Stearic acid Industrial stearic acid e) Wax Microcrystalline wax f) Anti-aging agent (A) Aromatic amine-based anti-aging agent N- (1,3-dimethylbutyl) -N ′ -Phenyl-p-phenylenediamine ("ANTAGE 6C", manufactured by Kawaguchi Chemical Co., Ltd.)
(B) 2,2,4-trimethyl-1,2-dihydroquinoline polymer ("Nonflex RD", manufactured by Seiko Chemical Co., Ltd.)
g) Sulfur 5% oil treated sulfur h) Vulcanization accelerator (A) Sulfenamide vulcanization accelerator N-cyclohexyl-2-benzothiazolylsulfenamide ("Noxeller CZ-G (CZ)", Ouchi Shinsei Chemical Industry)
(B) Thiuram vulcanization accelerator Tetramethylthiuram monosulfide ("Noxeller TS-P (TS)", manufactured by Ouchi Shinsei Chemical Co., Ltd.)

(Evaluation)
The evaluation was performed on rubbers obtained by heating and vulcanizing each rubber composition at 160 ° C. for 20 minutes using a predetermined mold.

<CTAB specific surface area (m ² / g)>
The measurement was performed according to ASTM D2663-69 (Method B).

<Number average molecular weight (Mn)>
The number average molecular weight was measured by GPC (gel permeation chromatography) and converted by standard polystyrene.
GPC device: manufactured by Shimadzu Corporation, LC-10A column: manufactured by Polymer Laboratories, (PLgel, 5 μm, 500 mm), (PLgel, 5 μm, 100 mm), and (PLgel, 5 μm, 50 mm), and three columns used in a linked manner Flow rate: 1.0 ml / min Concentration: 1.0 g / l Injection amount: 40 μl Column temperature: 40 ° C. Eluent: Tetrahydrofuran

<Dynamic magnification (dynamic spring constant / static spring constant)>
The dynamic magnification was calculated by measuring the dynamic spring constant and the static spring constant.

(1) Dynamic spring constant “Dynamic Servo” manufactured by Kinomiya Seisakusho Co., Ltd. was used as a measuring instrument, and the initial strain was 10%, the frequency was 100 Hz, and the amplitude was ± 0.05 mm, and was calculated by the calculation method described in JIS K 6394.

(2) Static spring constant "Tensilon" manufactured by Orientec Co., Ltd. is used as a measuring instrument, and compression between 0 and 5 mm is performed twice on a vulcanized rubber test piece of 50 mmφ x 25 mm at a crosshead speed of 10 mm / min. Repeatedly, a second load-deflection diagram was drawn and calculated based on the following formula (1).

(Static spring constant (N / mm)) = (w2-w1) / (δ2-δ1) (1)
(In the above formula (1), w1; load (N) when the deflection amount δ1 is 1.3 mm, w2; load (N) when the deflection amount δ2 is 3.8 mm)
The dynamic magnification was calculated based on the calculated dynamic spring constant and static spring constant. Index evaluation is performed with the dynamic magnification of Comparative Example 1 as 100, and the smaller the index is, the lower the dynamic magnification is, and the better the vibration isolation performance is. The evaluation results are shown in Table 1.

<Durability>
As a test piece for the durability test, a thick cylindrical metal fitting having an outer diameter of 16 mm and a height of 70 mm is positioned at the axial center of the thin cylindrical metal fitting in an inner hole of a thin cylindrical metal fitting having an outer diameter of 81 mm and a height of 49 mm. In addition, the cylindrical metal fittings having a structure in which both the cylindrical metal fittings are integrally connected with a new vulcanized rubber were used. In these test pieces, the vulcanized rubber connecting the two cylindrical fittings has a length of 38 mm, the width of the portion connecting the two cylindrical fittings is 22 mm, and the width of the portion fixed to the thick cylindrical fitting is 36 mm. Was set to be. The test piece having such a structure was subjected to constant excitation at a frequency of 3 Hz with a load corresponding to an initial displacement of ± 14 mm, and the number of vibrations until the vulcanized rubber was broken was measured. Index evaluation was performed with the number of vibrations of Comparative Example 1 as 100, and the larger the index, the better the durability. The evaluation results are shown in Table 1.

From the results in Table 1, it can be seen that the anti-vibration rubbers obtained from the rubber compositions according to Examples 1 to 3 have both a reduction in dynamic magnification and an improvement in durability. On the other hand, since the vibration-proof rubber obtained from the rubber composition according to Comparative Example 2 has a low number average molecular weight of natural rubber, durability is not improved much compared to Examples 1 to 3, and dynamic ratio is also high. It turns out that it is not reduced so much. Since the vibration-proof rubber obtained from the rubber composition according to Comparative Example 3 has a CTAB specific surface area (m ² / g) that is too large, the dynamic magnification is deteriorated. Furthermore, since the anti-vibration rubber obtained from the rubber composition according to Comparative Example 4 had a CTAB specific surface area (m ² / g) that was too small, the durability deteriorated.

Claims (2)

In the rubber composition for vibration-proof rubber obtained by mixing the carbon black-containing slurry solution and natural rubber latex in a liquid phase and drying,
The carbon black has a CTAB specific surface area (m ² / g) of 20 to 55, and carbon black measured in accordance with ASTM D2663-69 (Method B) in the rubber composition for vibration-proof rubber. The degree of dispersion is 98% or more,
A rubber composition for vibration-proof rubber, wherein the natural rubber has a number average molecular weight of 1.8 million or more.   An anti-vibration rubber obtained by vulcanization and molding using the rubber composition for anti-vibration rubber according to claim 1.